Look carefully on title here and there - UCS and UDK. UCS - Ultima Client Shell and UDK - Ultima Developer Kit. This are 2 different projects, second really is open source its goal is to create better and modern alternative to UltimaSDK library, Fiddler editor and provide to developers API with special controlls for creating different tools related with UO, like RegionEdit or GumpStudio and so on. UDK was and still is opensource, it was started by me and Xen. I take part on low level code and API while Xen have to take care about controlls and GUI. Unfortanly he leave project as have no more time for UO in his life. Without GUI part, development on this project slows down and I focused now near small console utility. It will be perfect if someone will take part on GUI, in that case I with pleasure return to active development...

As alternative I'm thinking about clearing most of code and resurecting project on GDI. By the way UDK was the main reason for deprecated other mine project - Fiddler+.

Anyway UCS don't use any code from UDK, and written mostly on C\C++ and assembler. Even more UCS project is older then UDK, as I remember we just start UDK when I was working on first public version of UCS (versions 0.5.00-0.6.00). I remember this as it was much dificulties to separated data and new protections for using it in different projects and it was first releases where UCS looks like it looks now.